I got pulled into 'Reincarnation Coliseum' because the visuals hit a very specific vibe, and the first thing I wanted to know was who drew it. After poking around the usual places—the publisher's product page, the credits in the physical volume, and databases like MangaUpdates and MyAnimeList—the clearest route to a definitive name is the tankōbon (or official volume) credits. For some series the artist is obvious on promotional art, but for others the illustrator credit can be buried in small print or only shown on the publisher's Japanese/Korean page.
From my digging, there isn’t a single, widely-circulated English-language source that lists the artist for 'Reincarnation Coliseum' by name in a way that’s reliably citable, which means the safest bet is to check the official publisher page for the edition you have, or the front/back matter of a printed volume. Scanlation groups sometimes list the mangaka or artist, but those credits can be inconsistent. Personally I like to cross-reference three places: the physical volume credits, the publisher's webpage, and a reputable manga database—when all three line up, I trust that name. For now, the artist credit for 'Reincarnation Coliseum' is best confirmed directly from the official release; I found that process oddly satisfying, like a mini detective hunt, and it made me appreciate the art even more.